diff --git a/pysnooper/pysnooper.py b/pysnooper/pysnooper.py
index cff1814..917fe00 100644
--- a/pysnooper/pysnooper.py
+++ b/pysnooper/pysnooper.py
@@ -1,9 +1,10 @@
 # Copyright 2019 Ram Rachum.
 # This program is distributed under the MIT license.
 
+from future import standard_library
+standard_library.install_aliases()
 import sys
 import os
-import pathlib
 import inspect
 import types
 import datetime as datetime_module
@@ -20,26 +21,31 @@ from .tracer import Tracer
 def get_write_function(output):
     if output is None:
         def write(s):
+            s += '\n'
+            if isinstance(s, bytes): # Python 2 compatibility
+                s = s.decode('utf-8')
             stderr = sys.stderr
             stderr.write(s)
-            stderr.write('\n')
     elif isinstance(output, (pycompat.PathLike, str)):
-        output_path = pathlib.Path(output)
         def write(s):
-            with output_path.open('a') as output_file:
+            s += '\n'
+            if isinstance(s, bytes): # Python 2 compatibility
+                s = s.decode('utf-8')
+            with open(output_path, 'a') as output_file:
                 output_file.write(s)
-                output_file.write('\n')
     else:
         assert isinstance(output, utils.WritableStream)
         def write(s):
+            s += '\n'
+            if isinstance(s, bytes): # Python 2 compatibility
+                s = s.decode('utf-8')
             output.write(s)
-            output.write('\n')
             
     return write
     
     
 
-def snoop(output=None, *, variables=(), depth=1):
+def snoop(output=None, variables=(), depth=1):
     write = get_write_function(output)
     @decorator.decorator
     def decorate(function, *args, **kwargs):
diff --git a/pysnooper/tracer.py b/pysnooper/tracer.py
index 497be6b..e693ee0 100644
--- a/pysnooper/tracer.py
+++ b/pysnooper/tracer.py
@@ -7,14 +7,15 @@ import re
 import collections
 import datetime as datetime_module
 
-def get_shortish_repr(item) -> str:
+import six
+
+def get_shortish_repr(item):
     r = repr(item)
     if len(r) > 100:
         r = '{r[:97]}...'.format(**locals())
     return r
 
-def get_local_reprs(frame: types.FrameType, *,
-                    variables=()) -> dict:
+def get_local_reprs(frame, variables=()):
     result = {}
     for key, value in frame.f_locals.items():
         try:
@@ -40,7 +41,7 @@ def get_local_reprs(frame: types.FrameType, *,
 
 source_cache_by_module_name = {}
 source_cache_by_file_name = {}
-def get_source_from_frame(frame: types.FrameType) -> str:
+def get_source_from_frame(frame):
     module_name = frame.f_globals.get('__name__') or ''
     if module_name:
         try:
@@ -85,7 +86,8 @@ def get_source_from_frame(frame: types.FrameType) -> str:
             if match:
                 encoding = match.group(1).decode('ascii')
                 break
-        source = [str(sline, encoding, 'replace') for sline in source]
+        source = [six.text_type(sline, encoding, 'replace') for sline in
+                  source]
 
     if module_name:
         source_cache_by_module_name[module_name] = source
@@ -94,8 +96,7 @@ def get_source_from_frame(frame: types.FrameType) -> str:
     return source
 
 class Tracer:
-    def __init__(self, *, target_code_object: types.CodeType, write: callable,
-                 variables=(), depth: int=1):
+    def __init__(self, target_code_object, write, variables=(), depth=1):
         self.target_code_object = target_code_object
         self.write = write
         self.variables = variables
@@ -112,8 +113,7 @@ class Tracer:
         sys.settrace(self.original_trace_function)
         
 
-    def trace(self: 'Tracer', frame: types.FrameType, event: str,
-              arg):
+    def trace(self, frame, event, arg):
         
         ### Checking whether we should trace this line: #######################
         #                                                                     #
diff --git a/requirements.txt b/requirements.txt
index a1cabb9..b34828c 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,2 +1,3 @@
 decorator>=4.3.0
-future>=0.17.1
\ No newline at end of file
+future>=0.17.1
+six>=1.12.0
\ No newline at end of file
diff --git a/setup.py b/setup.py
index af92292..0730306 100644
--- a/setup.py
+++ b/setup.py
@@ -3,8 +3,6 @@
 
 import setuptools
 
-with open('README.md', 'r') as readme_file:
-    long_description = readme_file.read()
 
 setuptools.setup(
     name='PySnooper',
@@ -12,15 +10,12 @@ setuptools.setup(
     author='Ram Rachum',
     author_email='ram@rachum.com',
     description="A poor man's debugger for Python.",
-    long_description=long_description,
+    long_description=open('README.md', 'r').read(),
     long_description_content_type='text/markdown',
     url='https://github.com/cool-RR/PySnooper',
     packages=setuptools.find_packages(),
-    install_requires=('decorator>=4.3.0',), 
-    tests_require=(
-        'pytest>=4.4.1',
-        'python_toolbox>=0.9.3',
-    ), 
+    install_requires=open('requirements.txt', 'r').read().split('\n'), 
+    tests_require=open('test_requirements.txt', 'r').read().split('\n'), 
     classifiers=[
         'Programming Language :: Python :: 3.6',
         'Programming Language :: Python :: 3.7',
diff --git a/tests/test_pysnooper.py b/tests/test_pysnooper.py
index 810ce40..5de04aa 100644
--- a/tests/test_pysnooper.py
+++ b/tests/test_pysnooper.py
@@ -40,7 +40,7 @@ def test_string_io():
     
 def test_variables():
 
-    class Foo:
+    class Foo(object):
         def __init__(self):
             self.x = 2
             
diff --git a/tests/utils.py b/tests/utils.py
index ce0e11a..638a098 100644
--- a/tests/utils.py
+++ b/tests/utils.py
@@ -11,7 +11,7 @@ import pysnooper.pycompat
 
 class _BaseEntry(pysnooper.pycompat.ABC):
     @abc.abstractmethod
-    def check(self, s: str) -> bool:
+    def check(self, s):
         pass
     
 class VariableEntry(_BaseEntry):
@@ -19,7 +19,7 @@ class VariableEntry(_BaseEntry):
         r"""^(?P<indent>(?: {4})*)(?P<stage>New|Modified|Starting) var:"""
         r"""\.{2,7} (?P<name>[^ ]+) = (?P<value>.+)$"""
     )
-    def __init__(self, name=None, value=None, stage=None, *,
+    def __init__(self, name=None, value=None, stage=None,
                  name_regex=None, value_regex=None):
         if name is not None:
             assert name_regex is None
@@ -35,7 +35,7 @@ class VariableEntry(_BaseEntry):
         self.value_regex = (None if value_regex is None else
                             re.compile(value_regex))
 
-    def _check_name(self, name: str) -> bool:
+    def _check_name(self, name):
         if self.name is not None:
             return name == self.name
         elif self.name_regex is not None:
@@ -43,7 +43,7 @@ class VariableEntry(_BaseEntry):
         else:
             return True
 
-    def _check_value(self, value: str) -> bool:
+    def _check_value(self, value):
         if self.value is not None:
             return value == self.value
         elif self.value_regex is not None:
@@ -51,14 +51,14 @@ class VariableEntry(_BaseEntry):
         else:
             return True
 
-    def _check_stage(self, stage: str) -> bool:
+    def _check_stage(self, stage):
         stage = stage.lower()
         if self.stage is None:
             return stage in ('starting', 'new', 'modified')
         else:
             return stage == self.value
 
-    def check(self, s: str) -> bool:
+    def check(self, s):
         match = self.line_pattern.match(s)
         if not match:
             return False
@@ -68,7 +68,7 @@ class VariableEntry(_BaseEntry):
 
 
 class _BaseEventEntry(_BaseEntry):
-    def __init__(self, source=None, *, source_regex=None):
+    def __init__(self, source=None, source_regex=None):
         if type(self) is _BaseEventEntry:
             raise TypeError
         if source is not None:
@@ -87,7 +87,7 @@ class _BaseEventEntry(_BaseEntry):
     def event_name(self):
         return re.match('^[A-Z][a-z]*', type(self).__name__).group(0).lower()
 
-    def _check_source(self, source: str) -> bool:
+    def _check_source(self, source):
         if self.source is not None:
             return source == self.source
         elif self.source_regex is not None:
@@ -95,7 +95,7 @@ class _BaseEventEntry(_BaseEntry):
         else:
             return True
 
-    def check(self, s: str) -> bool:
+    def check(self, s):
         match = self.line_pattern.match(s)
         if not match:
             return False